300 



LOWER VERTEBRATES. 



Order I.— MONOPNEUMONIA. 



The simple condition of the lung sac just alluded to is one of the most marked 

 characteristics of the family CeratouiDjE; the only member of the order. Years ago, 

 some fossil teeth were described, from the mesozoic rocks, as the type of the genus 

 Ceratodus, but, for a long time, these remained the only source of our knowledge of 

 the genus. In 1870 Mr. Gerhard Krefft described a living species of the genus {C. 

 forsteri) from the rivers of Queensland, Australia, and shortly afterward Dr. GUnther 

 of the British Museum described a second one ( C. miolepis) from the same regions. 

 These fishes have long been known to the natives, under the name barramunda, who 

 highly prized their salmon-colored flesh, and ate it without regard to the scientific 

 interest connected with the fish. The barramunda, or flat-head as the settlers call it, 

 reaches a length of about six feet, and a weight of twenty pounds. It frequents still 

 rivers, and feeds on the decaying leaves which fall from the trees and plants bordering 



Fig. 1G8.— Ctruloclus forsteri, barramunda. 



the banks. It is said at times to leave the water and go on the flats, but its traveling 

 powers cannot be great, as its weak fins seem scarcely able to support its weight, or 

 even to drag it along. The eggs are about the size of those of a newt, and, like them, 

 ai-e enclosed in a gelatinous envelope. Nothing is known of the developraent, but 

 this state of ignorance will not long remain, as naturalists are now on its track. 



Order II. — DIPNEUMONA. 



Like the last, this order contains but a single family, the Sirenid^. The species 

 ai'e evidently on a higher plane than Ceratodus, for the lungs are better developed, 

 and divided into two jjortions ; the gills are more reduced ; the fins smaller, and their 

 skeleton simplified. Two genera are known, one of which, Lepidosiren, comes from 

 the rivers of Brazil ; tlie other, Protopterus, from tropical Africa. Lepidosiren para- 

 doxa was discovered about fifty years ago, by Xatterer, an Austrian explorer. He 

 obtained only two specimens, one of which was about four feet in length. But very 

 few have since been found, and there is hardly any animal, specimens of which are so 

 much desired in zoological collections. It has the dorsal, caudal, and anal united into 

 one continuous fin ; the pectorals and ventrals reduced to a long and slender jointed 

 filament; and no external gills. It is said by the natives "to produce a sound not 

 unlike that of a cat, and to feed on the roots of the mandioca, and other vegetables." 

 Its teeth, however, are sharp and pointed, the molars having the cusps supported by 

 vertical ridges, facts which would indicate a diet of flesh, i-ather than of vegetable 

 nature. Some recent investigations, especially those of Dr. Howard Ayres, seem to 



